1. Field of the Invention
The present invention relates to a tape cartridge which rotatably accommodates a reel on which a recording tape, such as a magnetic tape or the like, is wound.
2. Description of the Related Art
Recording tapes such as magnetic tapes and the like are used as external recording media for computers and the like. Little space is required to accommodate such a recording tape at the time of storage thereof, and a large amount of information can be recorded thereon. A so-called single-reel recording tape cartridge is used in which a single reel, on which the recording tape is wound, is rotatably accommodated within a case.
Such a recording tape cartridge is provided with a braking means so that the reel does not rotate within the case at times when the recording tape cartridge is not being used (see Japanese Patent No. 3187022 for example). A recording tape cartridge equipped with such a braking means will be described on the basis of FIGS. 22 and 23.
In a recording tape cartridge 200 illustrated in FIG. 22, a single reel 204 is accommodated within a case 202. The case 202 has a gear opening 206 provided at the central portion of a floor plate 202A, and a rotation restricting rib 208 projecting downwardly from a ceiling plate 202B.
The reel 204 has a reel hub 210 which is formed in the shape of a hollow cylinder having a bottom, and around whose outer peripheral portion a recording tape is wound. A reel gear 214, which can mesh with a driving gear 212A formed at a rotating shaft 212 of a drive device, is formed in an annular form at the bottom surface of a floor portion 210A of the reel hub 210. Insert-through holes 216, which pass through the floor portion 210A, are provided at a plurality of positions spaced apart at uniform intervals on a circumference at the region where the reel gear 214 is formed. On the other hand, anchor projections 218 stand erect at the top surface of the floor portion 210A from plural places which are between the respective through holes 216 and are along a predetermined circumference (i.e., the anchor projections 218 are provided discretely). A gear tooth 218A is formed at the top end portion of each anchor projection 218.
A disc-shaped braking member 220 is provided so as to be inserted within the reel hub 210. A braking gear 220A, which is annular and which can mesh with the gear teeth 218A, is provided at the bottom surface of the braking member 220. The rotation restricting rib 208 of the case 202 is inserted in an insertion groove 222A of a projection 222, which stands erect from the top surface of the braking member 220, such that the braking member 220 cannot rotate with respect to the case 202 but can move upward and downward. Further, a compression coil spring 224 is disposed between the braking member 220 and the ceiling plate 202B of the case 202. There is usually a rotation locked state in which rotation of the reel 204 with respect to the case 202 is impeded due to the braking gear 220A of the braking member 220 meshing with the gear teeth 218A due to the urging force of the compression coil spring 224.
A releasing member 226 is disposed between the braking member 220 and the floor portion 210A of the reel hub 210, so as to abut each of the braking member 220 and the floor portion 210A. The releasing member 226 is formed in the shape of a plate which is substantially triangular as seen in plan view, so as to not interfere with the anchor projections 218. Leg portions 226A, which stand erect from the vertices of this substantially triangular plate, are inserted in the insert-through holes 216 of the reel 204.
When the leg portions 226A of the releasing member 226 are pushed by the driving gear 212A due to the operation of the driving gear 212A meshing with the reel gear 214, as shown in FIG. 23, the releasing member 226 is pushed up against the urging force of the compression coil spring 224 and pushes the braking member 220 upward. In this way, the meshing of the braking gear 220A and the gear teeth 218A, i.e., the state in which rotation of the reel 204 is locked, is released. In the state in which the meshing of the driving gear 212A and the reel gear 214 is maintained (i.e., in the state shown in FIG. 23), the releasing member 226 holds the braking member 220 at this released position.
When the rotating shaft 212 rotates, the reel 204 rotates within the case 202. At this time, the releasing member 226, whose leg portions 226A are inserted in the insert-through holes 216 of the reel 204, rotates integrally with the reel 204. A convex portion 226B, which is provided at the axially central portion of the releasing member 226, slidingly-contacts, in a state in which there is point-contact, a convex portion 220B which is provided at the axially central portion of the braking member 220 which cannot rotate with respect to the case 202. Note that both the braking member 220 and the releasing member 226 are formed by resin molding, and the complex configurations thereof can be easily obtained.
However, in recent years, higher recording densities have come to be required of the recording tape cartridge 200. In order to address such a requirement, it has been thought to make the recording tape more thin so as to increase the amount thereof which can be wound onto the reel 204. Further, accompanying the increase in speed of writing information onto the recording tape and reading information recorded on the recording tape, increasing the speed of the pulling-out of the recording tape (the feeding speed) has been considered. For these reasons, the recording tape cartridge 200 must be able to handle an increase in the time over which the reel 204 is continuously rotated, and an increase in the rotating speed of the reel 204.
However, in the above-described conventional recording tape cartridge 200, when the reel 204 rotates, the convex portion 220B of the braking member 220 which is made of resin, and the convex portion 226B of the releasing member 226 which is also made of resin, slidingly-contact one another. Therefore, if the rotational speed of the reel 204 is high (e.g., the speed of feeding the recording tape is 6 m/s or more) and such rotation is carried out over a long period of time, there is the concern that the convex portion 220B or the convex portion 226B will become worn or will melt. If the height of the convex portion 220B or the convex portion 226B becomes short due to such wear or the like, the meshing of the braking gear 220A of the braking member 220 and the gear teeth 218A of the reel 204 cannot be properly released within the stroke of movement of the rotating shaft 212.
Thus, in order to prevent wear between the braking member 220 and the releasing member 226, various conventional measures have been proposed. (Refer to Japanese Patent Applications Laid-Open (JP-A) Nos. 11-273307, 2002-197833, and 2000-339909).
JP-A No. 11-273307 discloses a recording tape cartridge in which the region of the releasing member 226, which region slidingly-contacts the convex portion 220B, is formed by a metal plate. This metal plate is fixedly mounted to the releasing member 226 by insert molding or adhesion.
JP-A No. 2002-197833 discloses a recording tape cartridge in which the region of one of the braking member 220 and the releasing member 226, which region slidingly-contacts the other of the braking member 220 and the releasing member 226, is formed by a metal member. This metal member is fixedly mounted to the one of the releasing member 226 and the braking member 220 by being fit therein or by being adhered thereto.
JP-A No. 2000-339909 discloses a structure in which a sheet member, which slides well, is interposed at the region of abutment between the braking member 220 and the releasing member 226. Specifically, this sheet member is adhered by an adhesive to the releasing member 226, and is made to slidingly-contact the convex portion 220B of the braking member 220.
In each of the aforementioned conventional structures, certain effects are obtained as countermeasures to the problem of wear between the braking member and the releasing member. However, there are the following drawbacks.
In the structure disclosed in JP-A No. 11-273307, because the metal plate also functions to reinforce the releasing member and aim for thinness, the metal plate must be provided over the entire surface of the releasing member. In a case in which the metal plate is fixed to the releasing member by insert molding, with merely a flat-plate-shaped metal plate, the strength of attachment is weak, and there is the concern that the metal plate may fall off of the releasing member due to a shock (the impact of a drop) at the time when the recording tape cartridge is dropped. Therefore, usually, in the case of insert molding, claw portions, which are embedded in the resin portion, are formed at the peripheral edge portion of the metal plate. However, the number of pressing processes for shaping the metal plate increases due to the formation of these claw portions (i.e., a bending process after punching is needed). Moreover, due to the need to make the releasing member thin, the claw portions of the metal plate are embedded in (the vicinities of) the regions where the leg portions 226A are formed. The positioning of the metal plate (the claw portions) with respect to the fixed mold used for insert molding (the leg portion 226A molding regions) is therefore complicated. For these reasons, the attaching of the metal plate to the releasing member by insert molding results in poor produceability. Moreover, in a case in which the metal plate is fixed to the releasing member by adhesion, the product yield is poor because, generally, it is difficult to adhere, by an adhesive, a material having good slidability, or the adhesiveness thereof is poor. Namely, produceability is poor also when the metal plate is attached to the releasing member by adhesion.
In the structure disclosed in JP-A No. 2002-197833, with respect to the case of using adhesion, the produceability is poor in the same way as in JP-A No. 11-273307. On the other hand, when a metal member is fixed to the releasing member or the like by fitting, claw portions for engagement, which are formed so as to be bent in a substantial V-shape from the peripheral edge portion of the flat-plate-shaped metal member, are provided so as to extend out, and fitting is carried out by these claw portions for engagement being inserted into holes for engagement, which are formed in the releasing member, while the claw portions for engagement deform. Therefore, in the same way as with the metal plate of JP-A No. 11-273307, the number of pressing processes for shaping the metal member increases (in particular, a bending process is added). Further, because the metal member is a relatively compact part, it is difficult to ensure dimensional stability due to the pressing processes. When the dimensional accuracy (the machining accuracy) of the claw portions for engagement deteriorates, it is difficult to insert the claw portions for engagement into the holes for engagement, or it is easy for the metal member to fall off of the releasing member due to the impact of a drop. Therefore, the product yield of the metal member, of which high dimensional accuracy is required, deteriorates. For these reasons, attachment of the metal member to the releasing member by fitting results in poor produceability.
In the structure disclosed in JP-A No. 2000-339909, the sheet member, which has good slidability, is fixed to the releasing member by adhesion. Therefore, in the same way as in the above-described case of the metal plate and the like, adhesion by an adhesive is difficult or the adhesiveness is poor, and the product yield is poor. In particular, because it is easy for warping or strain to arise at the sheet member due to the mechanical properties thereof (such as the sheet member being thin and having low rigidity, or the like), adhesion by an adhesive is even more difficult.